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The increased use of allograft tissue for musculoskeletal repair has brought more focus to the safety of allogenic tissue and the efficacy of various sterilization techniques. Gamma irradiation is an effective method for providing terminal sterilization to biological tissue, but it is also reported to have deleterious effects on tissue mechanics in a dose-dependent manner. At irradiation ranges up to 25 kGy, a clear relationship between mechanical strength and dose has yet to be established. The aim of this study was to investigate the mechanical properties of bone and soft tissue allografts, irradiated on dry ice at a low absorbed dose (18.3-21.8 kGy) and a moderate absorbed dose (24.0-28.5 kGy), using conventional compressive and tensile testing, respectively. Bone grafts consisted of Cloward dowels and iliac crest wedges, while soft tissue grafts consisted of patellar tendons, anterior tibialis tendons, semitendinosus tendons, and fascia lata. There were no statistical differences in mechanical strength or modulus of elasticity for any graft irradiated at a low absorbed dose, compared to control groups. Also, bone allografts and two soft tissue allografts (anterior tibialis and semitendinosus tendon) that were irradiated at a moderate dose demonstrated similar strength and modulus of elasticity values to control groups. The results of this study support the use of low dose and moderate dose gamma irradiation of bone grafts. For soft tissue grafts, the results support the use of low dose irradiation.

A correlation between extractable bone morphogenetic proteins (BMPs) in demineralized bone matrix (DBM) and osteoinduction has been suggested. Extractable BMP-4 and osteoinductivity of DBM from 40 donors were assessed using enzyme-linked immunosorbent assay (ELISA) and in vivo athymic mouse assay, respectively. Extractable BMP-4 level averaged 3.7 +/- 0.21 ng/g of DBM and correlated with osteoinductivity of the DBM in an in vivo assessment of induced newbone formation.